This invention relates to imprinting patterns on flat glass as it is being produced by the float process. More particularly, the invention relates to producing regular, distinct patterns without distorting the patterns.
The float process, in which molten glass is shaped into a flat ribbon as it passes along a pool of molten metal such as tin, has become the predominant technique for commercially producing flat glass. The process is adapted to producing glass surfaces having a polished appearance. Patterned glass does not require the quality surface finish provided by the float process, and, therefore, patterned glass is generally made by a rolling technique. Providing a separate facility for the exclusive production of rolled pattern glass can be difficult to justify economically in view of the relatively small market for patterned glass. It would be desirable if a float glass line could be modified to produce patterned glass during limited time periods while producing standard float glass the majority of the time.
Various proposals have been made in the prior art for creating patterns or otherwise modifying the surface of float glass during the forming process. U.S. Pat. Nos. 3,672,859 (Classen), 3,951,633 (Danihel) and 4,074,994 (Glikman et al.) disclose modifying the surface textures of glass ribbons in float forming chambers to produce random patterns. Because the patterns are random, the subsequent stretching of the glass ribbon that is part of the usual float forming operation does not have an objectional effect on the patterns. In fact, the Classen and Glikman patents cite this stretching as being useful in producing random surface effects. But for a distinctly shaped pattern, the distorting of this pattern would be objectionable. In U.S. Pat. No. 3,472,641 (Gray) distinct patterns are imparted to float glass by gas jets, and in U.S. Pat. No. 3,850,605 (Maltman et al.) discrete colored areas are created in float glass. In both of these it appears that the patterns would be subject to distortion by the inherent subsequent stretching of the glass ribbon, but no solution to this problem is disclosed.
U.S. Pat. No. 3,558,294 (Touvay) uses a roller to press wires into a float glass ribbon. It is disclosed that the temperature is such that the impressions made by the roller are subsequently leveled.
Patterned glass can also be made by etching or grinding patterns into individual sheets of glass after they have been formed. That approach, however, is labor intensive and, therefore, costly.
It would be desirable for an economical technique to be available for creating distinct patterns in float glass without subsequent distortion of the patterns.